[_pmf_]

I think it's a strong signal to industrial users that Python is a stable and mature language whose core developers care about practical usage. Pushing Python 3 for ideological reasons ("it's the right thing to do") would alienate a lot of users who have real work to do and cannot invest weeks to upgrade to a version that does not provide them any benefits.

[Rubikan]

If the Python core developers care so much about practical usage they should never have released python3 with features that break backwards compatibility.

Your argument is right, but they should have thought about that before fracturing the python community.

[_pmf_]

Yes; I suppose they will be more careful in the future.

The Java model of using separate lifecycles for the runtime/JVM and the language itself is probably a good role model for the future; it allows introducing new language features without any danger of creating library inconsistencies and allows specifying source and VM versions individually.